Problema Solution
A boat travels 7km upstream and 7km back. The time for the round trip is 10hrs. THe speed of the stream is 3 km/hr. What is the speed of the boat in still water?
Answer provided by our tutors
let
t1 = the time of the upstream trip
t2 = the time of the downstream trip
d = 7 km
v = the speed of the boat in still water
c = 3 km/h the speed of the current
the speed upstream is v - x
the speed downstream is v + x
since speed = distance/time => distance = speed * time
(v - 3)*t1 = 7
(v + 3)*t2 = 7
the time for the round trip is 10hrs
t1 + t2 = 10
by solving the system
(v - 3)*t1 = 7
(v + 3)*t2 = 7
t1 + t2 = 10
we find
v = 3.78 km/h
t1 = 8.97 h
t2 = 1.03h
the speed of the boat in still water is 3.78 km/h.